1. Field of Invention
This invention relates to measurement and testing for liquid analysis, and more particularly to determining electrically the quality of any natural or synthetic oil, oil substitute, oil additive, or any other nonpolar or weakly polar liquid.
2. Description of the Prior Art
Three well known methods of determining e.g. lubricating oil quality are infrared spectroscopy, pH measurement, and prediction of degradation. Measuring the quality of the oil by infrared spectroscopy has the advantage of determining many qualities of the oil other than lubricity. Unfortunately this method requires removing a sample of the oil from e.g. the automobile and placing it in an infrared spectroscopy instrument. The instrument is expensive and requires some dexterity and experience with scientific measurements to use. Thus this is not a suitable method for alerting one that the oil needs to be changed.
Although the pH of an oil gives an indication that something is wrong with the oil, the pH does not directly measure the oil lubricating quality, but merely measures the presence of acids in the oil. It does not determine that the oil has degraded if the oil is contaminated by water or metal particulate. Basing oil quality on pH can also be unreliable. Volatile acids can evaporate over extended periods at operating temperatures and give a pH reading inconsistent with oil quality. The pH sensor apparatus is expensive and not particularly suited for the environment of the oil pan of an internal combustion engine.
Prediction methods for oil degradation are simple. Based on the mileage of the vehicle, a light comes on telling one that the oil needs to be changed. This does not take into account the various qualities of oil that can be used, nor does it take into account the actual driving conditions that directly effect the oil condition. Further, it does not account for engine wear as a factor in oil degradation. This method has recently become more sophisticated; however it is still simply a prediction that provides no qualitative or quantitative information regarding actual oil condition.